The present invention relates to nuclear power reactor fuel bundles and, in particular, to an improved apparatus for the assembly and disassembly of such bundles.
In a typical nuclear power reactor, nuclear fission occurs within so-called "fuel rods"which are assembled in a parallel array into bundles, a multiplicity of which consitute the fuel core of a reactor. Heat from the nuclear fission reaction is taken up by a fluid (usually water) flowing along the outer surface of the rods. As the reactor operates, the fuel is gradually consumed, and it is necessary at periodic intervals to replace the fuel. However, only a minor fraction of the fuel rods are replaced at any one time, in order to avoid large variations in reactor operation. In the event of premature bundle failure or fuel inspection, it is necessary to remove the bundles and to disassemble them for repairs, replacement, or inspection of selected rods. Thus, the bundles may be adapted for easy disassembly by remote means, since they become highly raidoactive during the operation of the reactor.
A number of arrangements have been disclosed in the prior art for assembling nuclear power reactor fuel bundles. See for example, U.S. Pat. No. 3,431,170 and copending application Ser. No. 386,201, filed Aug. 6, 1973, now U.S. Pat. No. 3,953,287, the latter being assigned to the same assignee as the present application. Many of the prior art arrangements, however, require the removal of relatively small parts which is difficult to do by remote disassembly techniques. Any system for locking fuel rods in a fuel bundle should be as simple as possible, not only to reduce the cost of the locking system employed, but also to simplify the need for special tools and complicated procedures for the subsequent disassembly and reassembly of the bundles under remote control conditions. The possibility of losing parts during remote disassembly makes it highly desirable to provide a locking system which, preferably, need not be disassembled at any time after the initial assembly.
The structure of Ser. No. 386,201 avoids this difficulty, but it, as well as that of the patent, is only applicable to fuel assemblies in which the upper tie plate is loaded by springs which push it upwardly. There is need for a design which is readily operable remotely, which avoids separable parts and which is applicable to fuel assemblies in which the upper tie plate is rigidly mounted on the tie rods which hold it in place.
The present invention overcomes the deficiencies and disadvantages of the prior art and accomplishes the foregoing objectives by providing a novel and simple, inexpensive means of assembling a nuclear reactor fuel bundle.